The root of this problem is that the Dropbox ability to quickly sync is frail.

I've had similar issues many times over the years. A couple of points:

Yate maintains 10 (by default) backups of your settings. They can be quickly imported via Yate>Import Settings from Backup

If you start or close Yate with the Shift key held, the sync file is not loaded or saved. When you get an error loading the sync settings when starting Yate, close the app holding the Shift key. Wait a few seconds and try again. In my experience this always works.

The 'An error occurred in the destination for the data' is the extracted Mac error message. Not much to go on there. In system settings make sure that Yate has Full Disk Access. Also make sure that Yate is listed in Files & Folders. You'll have to search for these settings as their location in System Settings is OS version dependent.

Aside from using the Shift key (which you should remember), I also tend to write an out of bounds (oob) copy of the settings whenever I make a change which is critical to preserve. Essentially I manually export the settings to a known location. That way if DB messes up and I don't catch the fact,I know that the oob settings are available. I do it via an action. I have the path hardcoded in my action.

Basically create a one line action which is an Application Settings Management statement. There are only two settings in the statement. The top control must be: Export Application Settings. The text field contains the full path to the file to be written. If you select the text field, you can drag in the folder then add the filename. It must have a .plist or .zip filename extension. This is equivalent to doing a Yate>Export Settings ... but it's much faster as you don't have to select the file's location.